Rational construction of fluorescent molecular imprinted polymers for highly efficient glycoprotein detection

A HOF-101@AgNPs-based dual-signal mode aptasensor for electrochemiluminescence and fluorescence detection of E. coli O157:H7

Escherichia coli O157:H7 (E. coli O157:H7) emerges as a foodborne pathogen, emphasizing the imperative for creating precise detection tools. An ultrasensitive electrochemiluminescence/fluorescence (ECL/FL) dual-signal mode aptasensor was constructed for the detection of E. coli O157:H7. Ultrafine silver nanoparticles were loaded on the surface of hydrogen-bonded organic skeleton materials by in-situ photoreduction method, and then combined with aptamers that can identify specific targets to prepare HOF-101@AgNPs@Apt, greatly simplifying the ECL/FL dual-signal mode probe fabrication process and improving sensing reliability. HOF-101@AgNPs@Apt had both strong ECL luminescence and fluorescence, resulting in a high detection sensitivity. The low limit of detection (LOD) for ECL and FL were 0.48 CFU mL-1 and 2.39 CFU mL-1, respectively. Moreover, the proposed dual-signal mode aptasensor has been successfully applied to determine E. coli O157:H7 levels in tap water and milk with superior accuracy and high antiinterference capability, providing a promising method for food safety monitoring.

Chameleon-inspired molecular imprinted polymer with bicolored states for visual and stable detection of diethylstilbestrol in water and food samples

A novel biomimetic molecular imprinted polymer chip with fluorescence (FL) and structural (STR) states, inspired by color patterns of chameleon skin, is fabricated for detecting diethylstilbestrol (DES). The chip features a regularly structured, non-closed-packed (NCP) colloidal photonic crystal (CPC) lattice made monodisperse MIP spheres containing fluorescence poly ionic liquid (FPIL) pigments. The FL color originates from FPIL pigments and is further enhanced by the Purcell effect, while the STR color results from the periodic arrangement of the NCP CPC structure. Upon the addition of DES, the molecular imprinting recognition events of the chip induce bicolored responses. These color variations are observable to the naked eye. Based on a self-correction function of colors, the chip showed direct, sensitive (as low as 0.5 ng/mL), rapid (6 min), selective and stable detection of DES. In sample analysis, the results of DES detected by the chip were by which obtained by the HPLC-MS/MS method.

Carbon dot-based molecularly imprinted polymer fluorescent sensor for the detection of propranolol in plasma

Propranolol, a medication used to treat cardiovascular diseases, can be harmful when overdosed and hazardous to ecosystems if released into the environment. Here, a new molecularly imprinted fluorescent sensor was developed from carbon dots through a sol-gel method. Carbon dots served as both the fluorescent signal and the carrier, with propranolol as the template molecule and 3-aminopropyltriethoxysilane as the functional monomer to be grafted on carbon dots' surface. A novel detection method was established for the efficient, rapid, and cost-effective detection of propranolol in human plasma through quantitative analysis by using a fluorescence spectrophotometer and an ultraviolet spectrophotometer. Under the optimal conditions, the detection range of 0.5-4 mg L-1, the detection limit of 0.092 mg L-1, the imprinting factor of 2.42, and the detection response time of 2 min were achieved. The prepared carbon dot-based molecularly imprinted fluorescent sensor was proved to have a wide accurate linear range, low detection limit, and very short response time, and can detect lower analyte concentrations with higher detection accuracy.

High-sensitivity detection of glycoproteins by high-density boric acid modified metal-organic framework surface molecularly imprinted polymers resonant light scattering sensor

Glycoproteins are difficult to be detected by imprinting strategy due to their low natural abundance, high flexible conformation and large size. Herein, a high-density boric acid modified metal-organic framework (MOF) surface molecularly imprinted polymer (SMIP) resonant light scattering sensor was constructed for the high-sensitivity detection of target glycoproteins. A MOF with large specific surface area was selected as the substrate material to support the boric acid group with high loading density (4.66 %). The introduction of the boric acid group in the SMIP provided a high-affinity binding site for the recognition and binding of glycoproteins. Shallow surface cavities with rapid mass transfer (equilibrium time 20 min) were thus formed by surface imprinting. Furthermore, high sensitivity (limit of detection 15 pM) was achieved at physiological pH (7.4), which was conducive to the detection of glycoproteins with low natural abundance in complex biological samples and maintaining physiological activity.

A dual-capture-system polymer based on imprinted cavities and post-imprinting modification sites with significantly improved affinity and specificity for sialic acid and sialylated glycoprotein

The abnormal expression of N-acetylneuraminic acid (SA) and sialylated glycoproteins in biological fluids are closely associated with various diseases including cancer. However, the low content of SA and the strong interference of complex matrix greatly influence the effective capture of SA in biosamples prior to analysis. Herein, a dual-capture-system strategy based on molecular imprinting and post-imprinting modification (PIM) was proposed to precisely capture SA with improved binding affinity and specificity. After imprinting with SA as template, dynamic imine bonds are introduced by post-imprinting modification, enabling sufficiently high specificity to capture SA through imprinting cavities and the dynamic imine bonds hydrolysis reaction simultaneously. The prepared magnetic PIM polymers (Mag-MIPs-PIM) exhibited significantly high specificity both for SA (IF = 4.24) and sialylated glycoprotein (IFTRF = 3.50). In addition, the feasibility of Mag-MIPs-PIM for practical application was demonstrated by association with HPLC for the determination of SA in human serum, and an LOD of 0.01 × 10-2 g L-1 was obtained. The proposed strategy based on molecular imprinting and PIM provides a new inspiration for the improvement of selectivity of the molecularly imprinted polymers.

Lossy Mode Resonance Optical Fiber Enhanced by Electrochemical-Molecularly Imprinted Polymers for Glucose Detection

Noninvasive glucose sensors are emergent intelligent sensors for analyzing glucose concentration in body fluids within invasion-free conditions. Conventional glucose sensors are often limited by a number of issues such as invasive and real-time detection, creating challenges in continuously characterizing biomarkers or subtle binding dynamics. In this study, we introduce an efficient lossy mode resonance (LMR) optical fiber sensor incorporating the molecularly imprinted polymers (MIPs) to amplify glucose molecules. A molecularly imprinted recognition platform is created on an LMR sensor surface through a convenient one-step electrochemical (EC) polymerization method, in which 3-Aminophenylboric acid and glucose serve as the functional monomer and template molecule, respectively. LMR resonance wavelength shift induced by the coupling of the optical lossy mode and the fiber core mode is employed as the parameter to characterize biomolecules. Due to its high sensitivity to surrounding environment changes, a limit of detection (LOD) of 4.62 × 10-2 μmol/L for glucose can be achieved by this optical fiber sensor. Additionally, the prepared EC-MIPs LMR sensor is capable of detecting glucose molecules in human saliva samples with high accuracy, endowing its potential for practical applications.

Computational and Experimental Comparison of Molecularly Imprinted Polymers Prepared by Different Functional Monomers-Quantitative Parameters Defined Based on Molecular Dynamics Simulation

BACKGROUND

In recent years, the advancement of computational chemistry has offered new insights into the rational design of molecularly imprinted polymers (MIPs). From this aspect, our study tried to give quantitative parameters for evaluating imprinting efficiency and exploring the formation mechanism of MIPs by combining simulation and experiments.

METHODS

The pre-polymerization system of sulfadimethoxine (SDM) was investigated using a combination of quantum chemical (QC) calculations and molecular dynamics (MD) simulations. MIPs were prepared on the surface of silica gel by a surface-initiated supplemental activator and reducing agent atom transfer radical polymerization (SI-SARA ATRP).

RESULTS

The results of the QC calculations showed that carboxylic monomers exhibited higher bonding energies with template molecules than carboxylic ester monomers. MD simulations confirmed the hydrogen bonding sites predicted by QC calculations. Furthermore, it was observed that only two molecules of monomers could bind up to one molecule of SDM, even when the functional monomer ratio was up to 10. Two quantitative parameters, namely, the effective binding number (EBN) and the maximum hydrogen bond number (HBNMax), were defined. Higher values of EBN and HBNMax indicated a higher effective binding efficiency. Hydrogen bond occupancies and RDF analysis were performed to analyze the hydrogen bond formation between the template and the monomer from different perspectives. Furthermore, under the influence of the EBN and collision probability of the template and the monomers, the experimental results show that the optimal molar ratio of template to monomer is 1:3.

CONCLUSIONS

The method of monomer screening presented in this study can be extended to future investigations of pre-polymerization systems involving different templates and monomers.

Signal amplification in molecular sensing by imprinted polymers

In the field of sensing, the development of sensors with high sensitivity, accuracy, selectivity, sustainability, simplicity, and low cost remains a key focus. Over the past decades, optical and electrochemical sensors based on molecular imprinting techniques have garnered significant attention due to the above advantages. Molecular imprinting technology utilizes molecularly imprinted polymers (MIPs) to mimic the specific recognition capabilities of enzymes or antibodies for target molecules. Recently, MIP-based sensors rooting in signal amplification techniques have been employed to enhance molecular detection level and the quantitative ability for environmental pollutants, biomolecules, therapeutic compounds, bacteria, and viruses. The signal amplification techniques involved in MIP-based sensors mainly cover nucleic acid chain amplification, enzyme-catalyzed cascade, introduction of high-performance nanomaterials, and rapid chemical reactions. The amplified analytical signals are centered around electrochemical, fluorescence, colorimetric, and surface-enhanced Raman techniques, which can effectively realize the determination of some low-abundance targets in biological samples. This review highlights the recent advancements of electrochemical/optical sensors based on molecular imprinting integrated with various signal amplification strategies and their dedication to the study of trace biomolecules. Finally, future research directions on developing multidimensional output signals of MIP-based sensors and introducing multiple signal amplification strategies are proposed.

Magnetic molecularly imprinted polymer based on coordination for the determination of trace banned substance furosemide in human urine

Furosemide (FUR), banned in sports events by the World Anti-Doping Agency, is a key target in drug tests, necessitating a pretreatment material capable of selectively, rapidly, and sufficiently separating/enriching analytes from complex matrices. Herein, a metal-mediated magnetic molecularly imprinted polymer (mMIP) was rationally designed and synthesized for the specific capture of FUR. The preparations involved the utilization of chromium (III) as the binding pivot, (3-aminopropyl)triethoxysilane as functional monomer, and Fe3O4 as core, all assembled via free radical polymerization. Both the morphologies and adsorptive properties of the mMIP were characterized using multiple methods. The resulting Cr(III)-mediated mMIP (ChM-mMIP) presented excellent selectivity and specificity toward FUR. Under optimized conditions, the adsorption capacity reached 128.50 mg/g within 10 min, and the imprinting factor was 10.41. Moreover, it was also successfully applied as a dispersive solid-phase extraction material, enabling the detection of FUR concentration as low as 20 ng/mL in human urine samples when coupled with a high-performance liquid chromatography/photodiode array. Overall, this study offers a valuable strategy for the development of novel recognition material.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2021-2022

The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates is a well-established technique and this review is the 12th update of the original article published in 1999 and brings coverage of the literature to the end of 2022. As with previous review, this review also includes a few papers that describe methods appropriate to analysis by MALDI, such as sample preparation, even though the ionization method is not MALDI. The review follows the same format as previous reviews. It is divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of computer software for structural identification. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other general areas such as medicine, industrial processes, natural products and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. MALDI is still an ideal technique for carbohydrate analysis, particularly in its ability to produce single ions from each analyte and advancements in the technique and range of applications show little sign of diminishing.

Post-imprinting modification of molecularly imprinted polymer for proteins detection: A review

Inspired by protein post-translational modification (PTM), post-imprinting modification (PIM) has been proposed and developed to prepare novel molecularly imprinted polymers (MIPs), which are similar to functionalized biosynthetic proteins. The PIM involves site-directed modifications in the imprinted cavity of the MIP, such as introducing high-affinity binding sites and introducing fluorescent signal molecules. This modification makes the MIP further functionalized and improves the shortcomings of general molecular imprinting, such as single function, low selectivity, low sensitivity, and inability to fully restore the complex function of natural antibodies. This paper describes the characteristics of PIM strategies, reviews the latest research progress in the recognition and detection of protein biomarkers such as lysozyme, prostate-specific antigen, alpha-fetoprotein, human serum albumin, and peptides, and further discusses the importance, main challenges, and development prospects of PIM. The PIM technology has the potential to develop a new generation of biomimetic recognition materials beyond natural antibodies. It can be used in bioanalysis and other multitudinous fields for its unique features in molecule recognition.

Sensitive Electrochemical Sensor for Glycoprotein Detection Using a Self-Serviced-Track 3D DNA Walker and Catalytic Hairpin Assembly Enzyme-Free Signal Amplification

Approaches for the detection of targets in the cellular microenvironment have been extensively developed. However, developing a method with sensitive and accurate analysis for noninvasive cancer diagnosis has remained challenging until now. Here, we reported a sensitive and universal electrochemical platform that integrates a self-serviced-track 3D DNA walker and catalytic hairpin assembly (CHA) triggering G-Quadruplex/Hemin DNAzyme assembly signal amplification. In the presence of a target, the aptamer recognition initiated the 3D DNA walker on the cell surface autonomous running and releasing DNA (C) from the triple helix. The released DNA C as the target-triggered CHA moiety, and then G-quadruplex/hemin, was formed on the surface of electrode. Eventually, a large amount of G-quadruplex/hemin was formed on the sensor surface to generate an amplified electrochemical signal. Using N-acetylgalactosamine as a model, benefiting from the high selectivity and sensitivity of the self-serviced-track 3D DNA walker and the CHA, this designed method showed a detection limit of 39 cell/mL and 2.16 nM N-acetylgalactosamine. Furthermore, this detection strategy was enzyme free and exhibited highly sensitive, accurate, and universal detection of a variety of targets by using the corresponding DNA aptamer in clinical sample analysis, showing potential for early and prognostic diagnostic application.

Highly Efficient Selective Extraction of Chlorpyrifos Residues from Apples by Magnetic Microporous Molecularly Imprinted Polymer Prepared by Reversible Addition-Fragmentation Chain Transfer Surface Polymerization

Chlorpyrifos, as a moderate toxic organophosphorus pesticide, is prone to lingering in the environment and cannot be monitored easily. In this study, a magnetic, microporous, molecularly imprinted polymer was synthesized by using the reversible addition-fragmentation chain transfer polymerization method. The synthesized materials were properly characterized in terms of morphology, selectivity, and sorption capacity and used as sorbents for magnetic solid phase extraction for the selective determination of chlorpyrifos in apple samples. Results showed that the magnetic microporous molecularly imprinted materials were rough and porous spheres at an average size of 5 nm. The materials were highly selective toward chlorpyrifos with a superior sorption capacity of 167.99 mg·g^-1 and were resistant to the interference of competitive pollutants. After optimization, the recoveries of chlorpyrifos reached 96.2-106.5%, and the detection limit was 0.028 μg·kg^-1 by HPLC. Based on these analytical validation results, the developed method could be effective at determining chlorpyrifos in apples.

Magnetic Molecularly Imprinted Polymers for the Separation and Enrichment of Cannabidiol from Hemp Leaf Samples

Cannabidiol (CBD) has attracted immense attention due to its excellent clinical effects in the treatment of various diseases. However, rapid and accurate extraction of CBD from hemp plant concentrates remains a challenge. Thus, novel magnetic molecularly imprinted polymers (CBD-MMIPs) with specific recognizing capability for CBD were synthesized using ethylene glycol dimethacrylate as the cross-linker, CBD as the template, methacrylic acid as the functional monomer, azobisisobutyronitrile as the initiator, and Fe₃O₄ nanoparticles modified with SiO₂ as the magnetic carrier. The morphological, magnetic, and adsorption properties of obtained CBD-MMIPs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry, surface area and porosity analyses, and various adsorption experiments. The results showed that the CBD-MMIPs had selective specificity and high adsorption capacity for CBD. The adsorption of CBD by CBD-MMIPs could reach equilibrium in a short time (30 min), and the maximum adsorption capacity was as high as 26.51 mg/g. The specific recognition and selectivity properties of CBD-MMIPs to CBD were significantly higher than that of other structural analogues, and the regeneration tests established that the CBD-MMIPs had good recyclability. Furthermore, the CBD-MMIPs could be successfully used as an adsorbent to the extraction of CBD from hemp leaf sample concentrates with high recovery efficiencies (93.46-97.40%).